No Peaks The Interpretation of Diffuse Scattering

Diffuse scattering is always present in the SAXS of polymer materials. In Fig. 8.8 its most important components are sketched . The density fluctuation background re- 

If polymers are studied, approximately 90% of the SAXS intensity at the minimum of the curve or the anisotropic pattern is density fluctuation background. For metals the corresponding typical value is 10%. 

Other effects contribute to the diffuse scattering, as well. In particular, a smooth density transition zone between the phases (e.g., at particle surfaces) and a rough particle surface must be mentioned. 

The classical treatment of diffuse SAXS (analysis and elimination) is restricted to isotropic scattering. Separation of its components is frequently impossible or resting on additional assumptions. Anyway, curves have to be manipulated one-by-one in a cumbersome procedure. Discussion of diffuse background can sometimes be avoided if investigations are resorting to time-resolved measurements and subsequent discussion of observed variations of SAXS pattern features. A background elimination procedure that does not require user intervention is based on spatial frequency filtering (cf. p. 140). 

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